A typical flashlight has a casing, a light source and a power source in the casing, and a lens assembly mounted at a head end of the casing. The head-end lens assembly can be shifted longitudinally or axially of the casing relative to the light source to focus light emitted by the source into a controllable beam.
Such a flashlight as disclosed in U.S. Pat. No. 7,040,775 has a casing adapted to hold a battery, a battery-powered LED light source mounted on the casing and directed forward along an axis, and a holder sleeve axially displaceable on the casing forward of and relative to the LED light source. An image carrier, e.g. a slide or a mask, is fixed in the holder sleeve and axially aligned with the light source. An end piece on the casing forward of the LED light source and of the image carrier holds a lens. Thus axial displacement of the holder sleeve moves the image carrier relative to the light source and to the lens. For the displaceable support of the image carrier, in addition to the lamp head and the casing, at least three further connecting sleeves are provided, namely an adapter, a guide sleeve and a sliding sleeve, so that assembly of the flashlight is relatively complex.
Furthermore, flashlights are known in which the lamp head focuses the emitted light with a reflector it carries and the casing with the light source are connected to one another via a threaded connection such that the reflector and the light source can be displaced relative to one another by a rotary motion. However, this embodiment has the disadvantage that two hands are always required for focusing, the casing being held with one hand and the lamp head being rotated with the other hand.